1. Technical Field
The present disclosure relates to a connector to electrically connect a rotary body, a charging device incorporating the connector, and an image forming apparatus incorporating the connector.
2. Description of the Related Art
Typically, rollers or other such rotary bodies to which a voltage is applied, such as a charging roller, a development roller, and a transfer roller, are used in electrophotographic image forming apparatuses. As a known connector, the roller is electrically connected to a power supply via a shaft bearing. The bearing is made electrically conductive by dispersing electrically conductive material, such as carbon fiber, in plastic. Alternatively, the roller is connected to the power supply through the roller shaft at a single point.
FIG. 29A is a diagram illustrating a contact state in which a roller shaft 6a of a rotary body contacts a bearing 110x and FIG. 29B is a diagram illustrating a state in which a foreign substance is caught in a contact portion between the shaft 6a and the bearing 110x illustrated in FIG. 29A. As illustrated in FIG. 29A, in order to rotate the rotary body smoothly, a penetration hole 110a of the bearing 110x has an internal diameter that is greater than an external diameter of the shaft 6a. Therefore, the shaft 6a of the roller contacts the bottom of the bearing 110x. If a foreign substance X, such as trash, is caught in a contact portion between the bearing 110x and the shaft 6a along face (in face contact situation), as illustrated in FIG. 29B, the shaft 6a may be separated from the bearing 110x, which may cause a loss of power to the shaft 6a and the bearing. In the alternative connector in which an electrode contacts one end of the shaft of the rotary body at a single point, if the foreign object is caught in a contact portion between the shaft 6a and the electrode, electrical conductivity becomes lost, which may cause to be electrical conductive failure.
In proposed image forming apparatus JP-H07-219308-A, a charging device includes a first connector constituted by an electrode to contact a charging roller at a single point to supply a voltage (charging bias) and a second connector constituted by a bearing to contact the charging roller to contacts along a line to supply a voltage. FIG. 30 is a schematic diagram illustrating a configuration of the conventional charging device in the image forming apparatus in the present example. As illustrated in FIG. 30, an electrode 105 contacts a shaft end 6b of the shaft 6a of a charging roller 6 at a single point. A wire connected to the power supply 106 to apply the charging bias to the charging roller 6 bifurcates at an intermediate portion and one branch wire (first wire) 104a is connected to the electrode 105, and the other branch wire (second wire) 104b is connected to the electrically conductive bearing 110x. Therefore, the charging bias in a power supply 106 is applied to the charging roller 6 via a first power supply route including the electrode 105 and a second power supply route including bearing 110x. In this configuration, for example, if the foreign substance is caught between the shaft end 6b of the charging roller 6 and the electrode 105 and electrically-conducting failure occurs in the first power supply route, an electrically conductive state between the charging roller 6 and the power supply 106 can be kept so long as an electrically conductive state between the bearing 110x and the shaft 6a is kept. Accordingly, the present configuration can eliminate this type of power failure better than a configuration in which a single power supply route is provided.
However, in the above-described configuration, it is required to provide the first wire 104a to connect the electrode 105 and the second wire 104b to connect the bearing 110x, which requires more wiring space than a configuration in which only a single supply route is provided. In addition, it is necessary for the bearing 110x to be electrically conductive, which increases manufacturing cost.